The present invention relates to an image forming apparatus of an electrophotographic type for forming an image on an image-transfer material such as those used in a copying machine and a printer.
For an image forming apparatus such as an anolog type copying machine of a monocolor system employing an electrophotographic system, and a copying machine and a printer having therein a scanning system by means of a semiconductor laser and an LED, there have been proposals wherein a part of an image forming means is united to be a cartridge for replenishment or replacement, on occasion of consumption, of various kinds of photoreceptors, developer carriers, cleaning members and developer toners, each having their own lives, and primary portions of the aforementioned image forming means are united in a body which may be pulled out of the apparatus for maintenance or replacement. In addition, there have been proposals wherein a transport path for an image-transfer material on which an image is to be formed by an image forming means is opened so that the image-transfer material may be taken out easily for jam clearing.
As a typical example of the aforesaid constitution, there has been a proposal in Japanese Patent Examined Publication No. 54392/1983 wherein a photoreceptor drum, a developing unit and a cleaner are mounted solidly on a supporting member to be one unit so that the unit can be pulled out of the main body of an apparatus for easy replacement or maintenance of each unit. Further, in Japanese Patent Publication Open to Public Inspection No. 154255/1982 (hereinafter referred to as Japanese Patent O.P.I. Publication), the primary portions of an image forming means are united to be a disposable type, and in Japanese Patent O.P.I. Publication No. 147366/1984, there has been disclosed printer constitution wherein a disposable cartridge is used and a latent image is formed on a photoreceptor drum through scanning writing by means of dot exposure. Further, in those publications mentioned above, there have been disclosed separated shell structures wherein an upper half can be opened to cause a transport path for an image-transfer material to be accessible for clearing the jammed image-transfer material, and in the aforesaid Japanese Patent O.P.I. Publication No. 154255/1982, there has been disclosed a halved structure wherein a disposable process cartridge is provided on an upper half on a replaceable basis so that easy replacement of the cartridge and easy clearing of jamming may be attained. In Japanese Patent O.P.I. Publication No. 1161/1983, there has further been disclosed a technology wherein a halved structure is employed for easy replacement of a process cartridge mainly represented by a toner cartridge for replenishment and a cleaning cartridge for collected toners, and a process cartridge is provided in a lower half in particular for improvement of maintenance work.
Vertical types of the aforesaid structure have been disclosed in Japanese Patent O.P.I. Publication Nos. 244058/1988, 244059/1988, 244064/1988 and 179168/1989, and their aims are to attain the operations in the same direction and an improvement of jam clearing.
In Japanese Patent O.P.I. Publication No. 279870/1986, there has been disclosed an image forming apparatus wherein easy handling and operation of consumable supplies are attained and restriction of space for operation is reduced by causing the loading direction for image-transfer materials and the direction for loading or unloading of a process cartridge provided on an upper half to be the same.
When an operator moves movable portions to open the transport path for image transfer materials for securing the working space for jam clearing, the operator's work has been complicated and time-consuming. In addition, working space for jam clearing is narrow beyond expectation and a space for a hand for removing jammed sheets is not enough. An operator has opened a transport path for pinpointing jammed sheets based on the operator's judgment made from the display for a position of jam occurrence. However, when the transport path is complicated (especially, in case of image forming apparatuses for color, duplex, high speed or high-level functions), there are plural movable portions which need to be moved concurrently for opening the transport path. Thus, the operator has been puzzled and operated erroneously while wasting time, which has caused various problems. In addition, an image forming apparatus is generally installed at the height of the waist of an operator. Therefore, the operator has to locate the jammed sheet and clear it in an unnatural posture such as a half-sitting posture or a posture of leaning over, which results in inefficient work. Anyway, since an operator has to move movable portions for opening a transport path, work efficiency is not high and there is a risk of an injury on a human body when an operator puts all the strength of his body into his arms or when he inserts his hand into a narrow space.
On the other hand, when replacing process cartridges and cassettes, they have needed to be drawn far out of a main body of an apparatus and its work has been complicated in the past. In addition to that, considerable power has been required for an operator and he has sometimes dropped the process cartridges and cassettes because of their heavy weight and contact between a cassette and a sheet feeding roller. Namely, these jam clearing work and replacement work have been complicated and time-consuming, and it has been impossible to do the work in a simple and safe way, which has been a disadvantage.
When loading a process cartridge in or unloading it from a main body of an apparatus, it has been necessary that the apparatus is of a halved structure so that an inlet for a cartridge may be opened and closed. In addition to that, gears in a driving system linked with a photoreceptor and with a developing unit have been required to be set or removed easily and securely, resulting in a complicated structure of the main body of the apparatus and complicated handling and operation.